In order for metallocenes to be particularly useful in slurry type polymerization processes, it has generally been found necessary to form a catalyst system in which the metallocene and the cocatalyst are insoluble during the polymerization. Various approaches have been taken to provide insoluble heterogeneous catalyst systems that would be applicable. One technique involves the employment of metallocenes containing unsaturated substituents which can be prepolymerized in the presence of a cocatalyst to produce a solid insoluble catalyst system. An example of such a process is disclosed in U.S. Pat. No. 5,498,581.
Another approach for preparing such an insoluble heterogeneous catalyst system involves the employment of a special type of metallocene referred to as a metallocycle metallocene. A metallocycle type metallocene is one in which one of the cyclic dienyl groups that is pi bonded to the metal of the metallocene also contains a substituent which is sigma bonded to the metal of the metallocene. An example of such a metallocene is disclosed in U.S. Pat. No. 5,654,454. In that case, the metallocycle was produced by a hydrozirconation type reaction. Such compounds are referred to as metallocycles for the reason that there is what can be viewed as a cyclic structure comprising the cyclic dienyl group pi bonded to the zirconium and the substituent on the cyclic dienyl group being also bonded to the metal. It is believed that such compounds form self supported catalyst systems as a result of repeated ethylene insertions into the metal-substituent bond to result in a prepolymer having pendant metallocene groups.
An object of the present invention is to provide a new catalyst system comprising the product resulting from the combination of a cocatalyst and a metallocycle metallocene produced from a metallocene having an arylalkyl substituent on at least one of the cyclic dienyl groups of the metallocene by reacting the metallocene with two equivalents of an alkali metal alkyl.
Another object of the present invention is to provide a process for producing polymers from olefins comprising contacting an olefin with such a catalyst system under polymerization conditions.
Still another object of the present invention is provide a halogen-free metallocene capable of use as an olefin polymerization catalyst.
In accordance with the present invention, there is provided a method for producing metallocycle metallocenes which involves reacting a first metallocene having an aralkyl group, an aralkyldialkylsilyl, or an aryl dialkyl silyl group attached to a cyclodienyl group with about two molar equivalents of an alkali metal alkyl having at least 4 carbon atoms. (The term aralkyldialkylsilyl refers to groups of the formula xe2x80x94Rxe2x80x2xe2x80x3-Si(R)2xe2x80x94 wherein Rxe2x80x2xe2x80x3 is a alkylene radical having 1 to 2 carbon atoms in the chain between the two free valences of Rxe2x80x2xe2x80x3.)
In accordance with the present invention, one can produce metallocenes having the formula 
wherein L is a radical having a cyclodienyl skeleton, examples of which would include hydrocarbyl substituted and unsubstituted, cyclopentadienyl, idenyl, fluorenyl, and tetrahydroindenyl; Rxe2x80x2 is an aryl group, i.e. a cyclic compound having at least one six membered ring, examples of which would include phenyl, indenyl, fluorenyl, naphthyl, benzoindenyl, anthracenyl, phenanthracenyl, or the like, which could be hydrocarbyl substituted or unsubstituted; R is a divalent alkyl, alkyldialkylsilyl, or dialkylsilyl radical wherein the number of atoms separating L and Rxe2x80x2 is in the range of 1 to 3, Lxe2x80x2 is a hydrocarbyl substituted and unsubstituted radical having a cyclodienyl skeleton, examples of which would include cyclopentadienyl, indenyl, fluorenyl, and tetrahydroindenyl; Rxe2x80x3 is an aliphatic radical having 1 to 10 carbon atoms; and M is a transition metal, preferably Zr, Hf, or Ti. L and Lxe2x80x2 can optionally be connected to each other by a bridging structure. Examples of such bridging structures include divalent hydrocarbyl structures, preferably having 1 to 10 carbon atoms, such as dimethyl methylene, and dihydrocarbyl silyl structures, preferably having 2 to 10 carbon atoms, such as dimethylsilylene.
In certain case one can also use the present invention to form metallocenes of the formula 
wherein L is a cyclopentadienyl radical, each R is defined as above, and one Rxe2x80x2 is an indenyl radical and the other is an indanyl radical. Such metallocycles could be referred to as di-metallocycles or as double metallocycles. One specific example would be where each R is dimethylmethylene. Such a dimetallocycle can be produced by reacting bis(1-(n5-cyclopentadienyl)-1,1-dimethyl-1-(1-indenyl)-methane) zirconium dichloride with two equivalents of butyllithium. The resulting double metallocycle could be called (1-(n5-cyclopentadienyl)-1,1-dimethyl-1-indenyl)-methane) zirconium (1-(n5-cyclopentadienyl)-1,1-dimethyl-1-(1-indanyl)-methane), since in one ligand the zirconium is bonded to the cyclopentadienyl through pi bonds and to the indenyl through a sigma bond and in the other ligand the zirconium is bonded to the cyclopentadienyl through pi bounds and to the indanyl through a sigma bond, the indanyl having been formed because the hydrogen is not transferred in this case to the butene ligand but rather to the indenyl to form indanyl. Such a compound is illustrated as compound 187 in FIG. 2.
The resulting metallocenes can be used to as catalysts for the polymerization of olefins.